BMW and Zagato have peeled the lid off their Z4 coupe, springing a topless Z4 Zagato Roadster concept to world media at Pebble Beach.

The unveiling of the new convertible at the weekend's Pebble Beach Concours d'Elegance followed the release of a shadowy teaser image that left little to the imagination.

Pulled together in just six weeks, the Z4 Zagato Roadster carries over much of the coupe's styling, with the open-top cabin and low rear deck standing out as the main difference.

Images of the car's hideaway roof have not been released, although BMW confirms the Z4 Zagato Roadster utilises a fabric roof - another point of difference when compared to the regular Z4 and its folding hardtop.

The concept also benefits from a new rollbar design, which Zagato says was inspired by the wing of an airplane.

As with the coupe, the companies have not revealed details of the roadster's powerplant, although it is likely that the 250kW and 450Nm 3.0 litre turbo-six of the Z4 sDriv35is lurks under the long bonnet.

In the sDrive35is, the twin-turbo straight-six promises a 0-100km/h time of 4.8 seconds.

It remains to be seen if we'll see this concept, or the earlier coupe, make a limited-edition production debut.